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PATENTED FEB. 16, 1904.

. R. E. DUVALL. CUTTING TOOL.

UNITED STATES latented February 16, 1904.

PATENT OFFICE.

CUTTING-TOOL.

SPECIFICATION forming part of Letters Patent No. 752,211, dated February 16, 1.904.

Application filed November 12, 1903. Serial No. 180,933. (No model.)

To aZZ whom it may concern:

Be it known that I, ROBERT E. DUVALL, of Washington, District of Columbia, have invented a new and useful Improvement in Outting-Tools, of which the followingis a specification.

The object of this invention is to provide'a simple and effective tool bymeans of whicha previously-formed hole may be undercut or enlarged locally, preferably at its bottom, to the end that screw-threads may be cut throughout the length of the hole without injury to the tap.

In tapping holes where the opening does not extend through the metal, but is closed at its bottom, it is a well-known fact that the tap as it advances meets increased resistance due to the increasing density of the metal in advance of the tool, and as the bottom of the opening is approached the resistance is such as either to retard the further advance of the tap or fracture the same. To obviate this obj ectionable action, I have devised a cutting-tool of improved form and construction for the purpose of undercutting or enlarging the hole locally in order to relieve the packing of the metal in advance of the tap, and thus allow the same to out without undue resistance and Without danger of injury. 1

My improved cutting-tool embodies a cutting member adapted to rest on the bottom of the hole to be tapped and formed with a cutting-blade to act in the wall of the same and having an operating-stock adapted to be engaged with the cutting member-in such manner that the rotation of the stock will carry the member round with it, said parts being provided with cooperating surfaces of a relation and form that the pressure of the stock against the cutting member will urge the same radially and horizontally outward and force the cutting-blade into active relation to the wall of the hole, whereby the blade will form in the hole an annular groove or undercut.

In the accompanying drawings, Figure 1 is a side elevation of my improved tool with portions in section, showing the position of the cutting member in the hole before the member is forced outward. Fig. 2 is a similar view showing the cutting member forced outward to its full extent as it appears in action. Fig. 3 isa perspective View of the parts of the tool separated. Fig. tie a horizontal sectional plan View through the cutting member on the line a a of Fig. 1. Fig. 5 is a View illustrating the form of the hole after it is acted on by my improved tool. v

Referring to the drawings, 1 represents a cutting member, in the present instance in the form of a fiat plate, having a horizontal lower end 2 adapted to rest on the bottom of the hole and rounded, as shown at 8,Fig. 3, so as to move freely over the surface of the bottom as the plate is carried around in operation. At one side the lower end is' continued outward in the form of a lip 4, the end of which is suitably fashioned to form a cutting-tooth 5, which as the plate is urged outward in the hole will cut into the side 'of the same at its base. Above this lip the plate is formed with a straight edge or side 6, which by contacting with the side of the hole limits the outward movement of the plate and consequently the depth of out effected by the cutting-tooth. On its opposite side the plate is formed with an inclined surface 7, which is adapted to cooperate with a similarly-inclined surface 8 at the bottom of an open slot 9 in the end of an operating-stock 10, into which slot the plate loosely but snugly fits and by which it is carried around in the hole with the stock. On the pressure of the stock against the plate'the surface 8 acting against the inclined surface on the plate will urge the latter radially outward in a horizontal direction, forcing the cutting-tooth into the side of the hole, which tooth as it enters deeper and deeper will form an undercut or groove 11 therein, as shown in the drawings. This outward motion of the plate will continue until its straight side 6 encounters the side of the hole, whereupon its further outward motion will be arrested.

In the operation of the tool, the hole to be tapped being previouslyfformed by appropriate means, the cutting-plate is inserted therein, with its lower rounded edge resting I the bottom of the hole, and the slotted operau ing-stock is seated'o'ver the plate, as shown in Fig. 1. The stock is then rotated by suitable means and forced gradually downward against the plate, with its inclined surface 8 acting against the inclined surface 7 on the plate. As the parts continue to rotate and the downward pressureon the plate increases the latter is urged outward radially and horizontally along the bottom of the hole, causing the cutting-tooth to enter the side of the hole and resulting in the formation of the groove 11.

In order that when the operation is completed the cutting-plate may be conveniently removed from the hole, I propose to connect the plate with the operating-stock in such manner that while the plate may be moved radially with relation to the stock, as in operation, it will be con fined thereon and carried by the stock and will be automatically retracted when the stock is withdrawn from the hole. I prefer to effect this result by forming in the plate a slot 12, extending parallel with the inclined surface 7 through which slot passes a fastening-pin 13, fixed in the slotted end of the stock, the arrangement being such that when the stock is lifted or withdrawn the pin will act in the inclined-slot and will draw the plate radially inward from the position shown in Fig. 2 to that shown in Fig. 1, in which position of the parts, the cutting-tooth being free of the undercut or groove, the plate may be removed from the hole. While this construction is useful in practice and adds to convenience in handling and operating the tool, I do not deem it essential, for the tool may be operated with effectiveness without any connecting means between the stock and the plate.

Having thus described my invention, what I claim is 1. In a tool for undercutting previouslybored holes, the combination with a cutting member adapted to rest on the bottom of the hole and movable horizontally thereon, of an operating-stock adapted to be engaged loosely with said cutting member, said parts being formed with cooperating actuating-surfaces arranged to have a sliding engagement with each other, and adapted by pressure of the stock against the said cutting member to force the latter radially and in a truly horizontal direction outward.

2. In a cutting-tool the combination with a plate adapted to rest on the bottom of the hole and provided with an inclined surface and with a cutting-tooth, of an operating-stock formed to loosely engage the said plate and having an inclined surface adapted to cooperate with that on the plate, the relation of said surfaces being. such that pressure of the stock againstthe plate will automatically force the same radially outward.

In a cutting-tool the combination with a plate having a horizontal lower edge, a projecting cutting-tooth and an inclined surface, of an operating-stock formed with an open slot to receive the plate, said slot having an inclined bottom adapted to cooperate with the inclined surface of the plate.

4:. In a cutting-tool the combination with a radially-movable cutting member having a rounded horizontal lower inactive edge adapted to rest on the bottom of the hole, of an operating-stock adapted to be loosely engaged with said cutting member, said parts being formed with cooperating surfaces adapted by pressure of the stock on the cutting member, to urge the same radially outward.

5. In acutting-tool the combination with an operating-stock, of a cutting member mounted therein and movable radially outward by the pressure of the stock against the same, and operative connections between the stock and the plate acting automatically to retract the plate when the stock is withdrawn.

6. In a cutting-tool the combination with an operating-stock, of a cutting member mounted therein and movable radially outward by pressure of the stock against the same, said cutting member formed with an inclined slot, and a pin carried by the stock and engaging loosely in said slot.

In testimony whereof I hereunto set my hand, this 11th day of November, 1903, in the presence of two attesting witnesses.

ROBERT E. DUVALL.

Witnesses:

MARY A. WILSON, W. R. KENNEDY. 

